In nature, white-rot fungi, known lignin degraders, use plant matter as a source of nutrients, whereas the majority of microorganisms that live on plant matter do not degrade lignin. It is believed that lignin is a precursor of low-rank coals. A number of white-rot fungi are able to degrade low-rank coals as reported in the literature. See Cohen, et al., Applied Environmental Microbiology, 44: 23-27 (1982); Wilson, et al., Proceedings of the Tenth Annual EPRI Contractors Conference on Coal Liquefaction, May 6, 1986, Palo Alto, Calif.; Scott, et al., Biotechnology Progress, 2, 131-139 (1986); and Cohen, et al., Proceedings of the Direct Liquefaction Contractors Meeting, U.S. Department of Energy: Washington, D.C.; pages IV-48 to IV-64 (1986). The process of solubilizing low-rank coal with white-rot fungi has been termed "biosolubilization", indicating the metabolic origin of the soluble product. Work on biomineralization using German hard coals has been reported by Fakausa, Ph.D. thesis, Fredrich-Wilhelms University, Bonn, Federal Republic of Germany (1981); and the literature of bioconversion of coals, its relation to lignin degradation and work of lignin has been reviewed by Pyne and Wilson; Biological Coal Beneficiation Literature Review, Battelle Pacific Northwest Laboratory Report to the Electric Power Research Institute, May 1986.
However, the use of white rot broth cultures with the low-rank coal is not readily and economically adapted for production of useful products. Therefore it would be desirable to develop a method for the biosolubilization of low-rank coals in a cell-free environment which would be readily adaptable for use in industrial microbiological reactors or other readily available equipment.
It is therefore an object of the present invention to provide a method for producing a cell-free extract of white rot fungi comprising one or more enzymes which are capable of biosolubilizing low-rank coals.
It is a further object of the present invention to provide a method for biosolubilizing low-rank coals to a soluble product using a cell-free extract.
These and other objects of the present invention will be readily apparent from the following description, appended claims and by practice of the invention described herein.